1. Field of the Invention
The present invention relates generally to receiving apparatus and more particularly to a television on channel selecting apparatus in which the channel-selection can be carried out by a more simplified key operation.
2. Description of the Prior Art
The United States of America, for example, now employs a total of 125 channels for television broadcasting using general broadcast radio waves and CATV (cable television). The television receiver for receiving these television broadcasts is constructed as, for example, shown in FIG. 1. FIG. 1 is a block diagram of an overall circuit arrangement of this type of a conventional television receiver.
As FIG. 1 shows, a main antenna terminal 1 is connected to an antenna 51 which receives general television broadcast waves. The television broadcast waves received at the antenna 51 are supplied through the terminal 1 to a normal contact N of a switching circuit 3.
An auxiliary antenna terminal 2 is provided. This auxiliary antenna terminal 2 is connected with a tuner 53 for CATV and a CATV coaxial cable 52 is connected to the tuner 53 to supply therethrough CATV broadcast waves to the tuner 53. The tuner 53 selects, of the CATV broadcast signals, a broadcast signal on the channel according to the channel selection operation of a remote control commander (transmitter) 54. This signal is converted into a broadcast signal on a free channel of the general standard television broadcast channels, or example, channel 2. The converted signal is supplied through the terminal 2 to an auxiliary contact A of the switching circuit 3.
A control signal SW is generated from a microcomputer 10, which will be described later, to control the switching circuit 3 to select one of the broadcast signals supplied to the contacts N and A. The signal from the switching circuit 3 is supplied to a tuner circuit 4. The tuner circuit 4 is a preset-type electronic tuning tuner which selects the channel according to a channel selection signal CH from the microcomputer 10, and converts it into a video intermediate frequency signal.
The video intermediate frequency signal from the tuner circuit 4 is supplied through a video intermediate frequency amplifier 5 to a video detector circuit 6, from which the video signal is produced. This video signal is supplied to a video circuit or the recording system of a video tape recorder (VTR) though not shown.
The microcomputer 10 is employed for the channel selection and is connected with an antenna input change-over key 21, a channel-up key 22, a channel-down key 23, ten keys 24 and so on. As earlier noted, the microcomputer 10 produces data, i.e., the control signal SW and the channel selection signal CH. A receiving circuit 25 is provided to receive a remote control signal transmitted from an infrared type remote controller or commander 26. The commander 26 includes keys equivalent to, for example, the above-mentioned keys 21 to 24. The key output of the commander 26 is received by and supplied from the receiving circuit 25 to the microcomputer 10. To the microcomputer 10, is further connected light emitting diodes (LED) 27 which indicates the selected channel in a digital fashion.
A last-channel memory 11 is a last-condition memory which is connected to the microcomputer 10. The last-channel memory 11 is backed up though not shown so that when the power to the television receiver is turned off, the data in the memory 11 can be protected from being lost. In practice, the last-channel memory 11 is formed by a part of a random access memory (RAM) of the microcomputer 10.
The last-channel memory 11 when the power to the television receiver is turned off, stores the data CH of the channel selected by the tuner circuit 4 and the data SW indicative of the contact N or A selected by the switching circuit 3. When the television receiver is powered, the data SW and CH stored in the last-channel memory 11 are supplied to the switching circuit 3 and the tuner circuit 4. Thus, the channel selected until the power to the television receiver is turned off is again selected.
Upon channel-selection, the channel changed and the channel indication are effected as shown in FIG. 2.
Now, let it be assumed that the switching circuit 3 is connected to the contact N. Then, the broadcast signals received at the antenna 51 are supplied to the tuner circuit 4. If the channel-up key 22 is depressed, the data or signal CH is varied. Each time the channel-up key 22 is depressed, the tuner circuit 4 selects the next higher channel. If the channel-up key 22 is pressed continuously, for example, for more than 0.4 second, channel selection is made sequentially upward at a constant time interval. After selection of channel 125, channel 1 is next selected, thus all channels cyclically selected upward.
If the channel-down key 23 is depressed, or each time the down-key 23 is depressed, the next lower channel is selected, and if the key is continuously depressed, channel selection is made to progress downward. After channel 1 is reached, channel 125 begins, thus all channels cyclically selected downward.
When a desired channel number is inputted by the ten keys 24, the corresponding channel is directly selected in accordance with the channel selection signal CH. FIG. 2 shows the case in which while the channel 123 is being received, channel 6 is selected by the ten keys 24.
Accordingly, when the switching circuit 3 is in the contact N position, an arbitrary channel of the general television broadcast channels can be selected.
Meanwhile, if the output channel of the tuner 53, or channel 2 in that case, is selected by any one of the keys 22 to 24 and the change-over key 21 is depressed, the switching control signal SW controls the switching circuit 3 to be changed to the opposite position, i.e., from the contact N position to the contact A position, thus allowing the broadcast signals from the tuner 53 to be supplied to the tuner circuit 4. Thus, a desired channel of CATV broadcast can be selected by the operation of the commander 54.
If the change-over key 21 is further depressed, the switching control signal SW controls the switching circuit 3 to be changed to the opposite position in which the general television broadcasts can be received as described above. In this way, the above-mentioned television receiver can select any one of the general television broadcast channels and the CATV broadcast channels.
In the above-mentioned television receiver, however, when switching is made from general television broadcast to CATV broadcast, the switching circuit 3 is required to be controlled by the key 21 to change in position and the tuner circuit 4 must be controlled to receive the output channel of the tuner 53 by operating any one of the keys 22 to 24. Thus, the operation is cumbersome.
Also, in order to change the CATV broadcast into the general television broadcast upon reception, keys must be operated in like a manner and hence, the cumbersome key operation cannot be avoided.